1. Field of the Invention
The apparatus and method of the invention are directed to profile stitching such as found in embroidery operations, and the like, and more specifically to program controlled stitching apparatus and methods.
2. Description of the Prior Art
Present embroidery machines may be thought of as comprising five basic components. Such components include a pattern reader, a mechanical motion mechanism, a motion table, connecting devices including a synchronizing device and a stop motion and, finally, the sewing heads. The typical pattern reader is a slow and mechanically unstable pin reader. The mechanical motion mechanism is typically a Jacquard motion mechanism which limits operational speed to about 400 strokes per minute which effectively eliminates incentive operations on a majority of designs. Furthermore, such design inherently causes adjustments to affect the stitch length which results in varying performance from machine to machine. It is also to be noted that the mechanics of the typical Jacquard motion mechanism inherently requires nearly instantaneous acceleration of the pantograph which, in turn, places severe strain on the thread. Other deficiencies of conventional embroidery machines are found in the motion table, i.e., the pantograph, which exhibits varying motions end to end and which increase as the motion table wears from use. Furthermore, as the motion table wears, a lag develops in its ability to reverse and no adjustment is available.
Another deficiency to be found in the conventional embroidery equipment relates to synchronization which with the conventional Jacquard amounts to a trial and error technique resulting in additional down time when repairs are needed. The conventional synchronizing device is typically a mechanical cam on the main shaft of one of the sewing machines. Positioning is, thus, highly restrictive since the shaft-gear machine connection is required to be made through the machine heads. The drag of this mechanism, in turn, requires a jog mechanism to raise the needle to true dead center or at least clear of the fabric on command to stop. The conventional stop motions also exhibit frequent failures which result in either extensive repair or unrepairable garments when threaded breaks occur.
From the foregoing description of the so-called "Gross" and similar machines, it can be seen that there is a need to replace the slot and mechanically unstable pin reader and to provide an embroidery mechanism capable of functioning at higher speeds and with a substantial increase in average time to failure. Further, the capability of self-repairing embroidery and in-house pattern making would be desirable features in an improved embroidery mechanism. Also to be desired is a control mechanism which would allow controlled acceleration and deceleration of the motion table and with improved means for synchronization of the extent and speed of table motion with the sewing head needle speed and position.
Programmable and reprogrammable memory devices have also been used with other types of automatic embroidery machines and sewing apparatus. U.S. Pat. Nos. 3,385,244 and 3,385,245 illustrate the prior art practice of utilizing magnetic tape for pattern storage and reading. U.S. Pat. Nos. 3,872,808; 3,982,491; 3,986,466; 4,051,794 and 4,074,642 illustrate use of solid state memory with program controlled stitching mechanisms. With these more recent developments, there is still a requirement for some better form of electrical drive to replace the mechanical linkages of the older Jacquard-type readers. For example, it may be noted that in U.S. Pat. Nos. 3,385,244 and 3,385,245 an open loop stepping motor arrangement is employed which has many disadvantages, both with respect to the open loop character as well as with respect to use of stepping motors.
A common characteristic of both the old as well as the more recent pattern stitching apparatus is that such apparatus reads and reacts sequentially to pattern data only. It would obviously be more desirable to have the apparatus adapted to react non-sequentially as well in order to react to non-stitching responses such as thread breaks, incomplete X-Y motions, repair needs, power failure, and the like. It would also be desirable for the stitching apparatus not to be limited to special purpose applications and to provide, for maintenance purposes, program routines and mechanism for checking proper operation and locating sources of improper operations and causes of defects. These last-mentioned features have been noticeably lacking in the most advanced known prior art.
In any garment sewing operation involving profile stitching considerable time is involved in placing and removing the work. Prior art multiple head machines have recognized this problem by providing work frames which can be removed and loaded while a sewing cycle is in operation. On single head machines, means have been provided to cause the work holder to open at the end of the cycle but the work holder remains captive to the motion. Sometimes it is not desirable to release the sewn fabric. Therefore, it would be desirable, particularly for multiple head machines, to have a pattern controlled release independent of any particular point in the cycle to fit a variety of sewing conditions.
Another aspect of the prior art of interest to the invention concerns the relation of the table motion to the motion of the needle. In one type of prior art apparatus, the X-Y table is always in motion and this type of apparatus allows for deflection of the needle or the fabric or both since the fabric is in motion during the time of entry of the needle in the fabric. Such needle deflection inherently requires very heavy fabric clamping mechanisms to avoid fabric shifting during stitching. In another type of prior art apparatus, it is known to command X and Y motions when the needle is out of the fabric and this type apparatus therefore theoretically should not subject the needle or the fabric to bending or distortion. However, in the more advanced program controlled prior art profile stitching apparatus stepping motors are employed and no means is provided to insure that X and Y motions are completed prior to needle entrance. Therefore, the same needle deflection and fabric distortion can occur at the terminal part of the X-Y motion. As exemplified in U.S. Pat. No. 3,982,491 (see column 11), an attempt has previously been made to approximate a kind of protection to prevent needle deflection and fabric distortion by imposing severe limitations on maximum stitch length. With the foregoing in mind, it would be desirable to provide a program controlled stitching apparatus designed to insure that needle deflection and fabric distortion cannot occur and without such severe stitch limitations.
Other deficiencies in the prior art may also be observed. For example, since even the most modern program controlled stitching apparatus is basically equipped to read only pattern data and a very limited set of basic machine controls, the translation of the stored pattern data and the machine responses are obtained by handwired electrical circuitry. Therefore, a control pulse must and can only follow a pre-wired path and must provoke a predetermined response established by a wired circuit. Prior to the present invention, there has been no known program controlled stitching apparatus having means for receiving single or plural control pulses, analyzing with stored program logic the relation between such pulses and other operating conditions and using computer control rather than the pulse or pulses to determine the response. For example, the type of automatic sewing machine described in U.S. Pat. No. 4,051,794 requires the workpiece movement to be triggered directly with the needle signal and also requires in each stitch instruction a sew, no-sew command. Such a totally synchronized operation is characteristic of the most advanced known prior art automatic sewing mechanism. Yet, this type of operation imposes many undesirable limitations.
Note may also be taken here of prior art examples of machines which can physically read dimensions of a workpiece or of a drawing of the workpiece and convert such data into stitch coordinates. U.S. Pat. Nos. 4,073,247 and 4,074,642 illustrate this type of operation. While the systems described in these patents utilize a computer architecture or solid logic to translate signals to their positioning drive systems, the systems of these patents continue to exhibit the sequential use of memory as previously mentioned. The systems in these patents also read and react to pattern data only. The systems of such patents also continue the prior art practice of using any control pulses from the sewing apparatus directly to initiate the next stitch cycle. The elimination of all of these prior art limitations, i.e., sequential use of memory, reading and reacting to pattern data only, and using control pulses to initiate the next stitch cycle, constitutes one of the objects of the present invention.
The prior art automatic sewing mechanisms have also been limited because of being dependent on digital responding motors, i.e., stepping motors. For reasons which will become apparent as the description proceeds, such stepping motors are inherently unsuited to a multi-head sewing operation under program control as contemplated by the present invention. In this regard, it can be observed that stepping motors have limited torque, especially when operating at high speeds. Therefore, when applied to control of an X-Y motion table, the motion table mass is critical and must be low. Extremely complex motion table constructions are employed to reduce such mass. While an automatic sewing mechanism such as described in U.S. Pat. No. 4,051,794 has offered an improvement in increased speed as well as improved sewing capability through the substitution of solid state digital memory for the prior art mechanical mechanisms, the dependency on stepping motors and the direct synchronization between the sewing head and the workpiece through wired electrical circuitry has remained.
The more advanced prior art automatic sewing mechanism has employed randomly addressable storage. However, such random capability has not been fully utilized. For example, the prior art automatic program control apparatus has not provided the ability to change patterns in a single memory for execution using a relatively inexpensive storage media for retention. Further, the prior art program controlled mechanisms have not allowed patterns to be modified directly in the machine for correction purposes or for development of new patterns. Additionally, to the extent the prior art program controlled apparatus has utilized memory, such memory has not been conveniently adapted for adding new machine commands as required or for modifying existing program parameters. The sequential reading characteristic of prior art mechanisms has precluded the use of any type of repair cycle or the use of a repeat instruction for data compaction. In prior art apparatus, as illustrated for example in U.S. Pat. No. 4,051,794, the machine is stopped by a thread break signal and the operator must choose either to totally rerun the pattern or allow the gap to remain. A repair cycle would obviously offer an advantage in time and material savings. Furthermore, the open loop positioning control system used in the more advanced sewing mechanism such as in U.S. Pat. No. 4,051,794 does not provide for a signal to be returned from the stepping motors to insure the obtaining of a correct position. Since stepping motors are known to at least occasionally fail to react to one or more pulses, a homing cycle and associated hardware has been necessary to insure a correct start at the beginning of a pattern. It would, of course, be desirable to eliminate the need for such a homing cycle and such becomes another purpose of the present invention.
While controlled acceleration-deceleration closed loop servo controls have been used in various machine tool control systems, it has not been known, so far as applicants are aware, to provide a program controlled stitching apparatus adapted to use of such a control and adapted to the unique conditions encountered in profile stitching. More specifically, the prior art has made no provision in stitching apparatus for use of DC digital control with controlled acceleration independently on the X and Y motions so as to cause the motion table to traverse a least time path in combination with substantially uniform thread tension as opposed to straight line hypotenuse moves traversed by stepping mechanisms of the type found in the prior art. The lack of controlled acceleration has also led to frequent thread breaks due to abrupt stresses on the thread. Program controlled sewing mechanisms of the prior art have also had limitations in stitch speed, stitch length, the ability to make repair motions, the ability to move without sewing, the ability to perform sewing operations which are not "closed" such as in pocket flap operations, and the like, and in the ability to operate with different stitch speeds in different parts of the pattern. While prior art apparatus have used memory for pattern storage and have to some extent controlled fabric motion and stitching action independently, such apparatus have not used stored logic control in the manner of the present invention to provide the ability to control speed as well as movement of the motion table in both X and Y directions, the stitch length and the sewing head speed independently and simultaneously in coordination with the pattern.
Another general observation that can be made, in the light of the many prior art deficiencies enumerated above, is that for the most part all prior art program controlled profile stitching apparatus has been directed to high volume, special purpose applications. In style conscious garment operations there is clearly a need for a program controlled profile stitching apparatus that can rapidly and inexpensively be adapted to a variety of kinds of work without severe size limitations or extensive mechanical modifications.
While other comparisons might be made with the prior art, it is believed that the foregoing is sufficient to illustrate some of the deficiencies of the conventional as well as of the more recent programmable and reprogrammable sewing devices found in the prior art. The overcoming of all such deficiencies and the providing of new features and functions now heretofore achieved constitute objects of the present invention.